This application is based on and incorporates herein by reference Japanese patent application No. 2000-79700 filed Mar. 22, 2000.
1. Field of the Invention
The present invention relates to a motor device in which a commutator and brushes are disposed in a reduction unit outside a yoke.
2. Related Art
In a conventional motor device, an electric motor unit has a cylindrical yoke and a rotor, and a reduction unit including reduction gears therein is coupled to the yoke. The rotor is primarily comprised of a rotary shaft for driving the reduction gears, an armature, a cylindrical commutator and elongate brushes. The armature and the commutator are fixed to the rotary shaft and arranged in the axial direction of the rotary shaft. The brushes are spring-biased to contact the commutator in the radial direction of the commutator. The rotor is entirely accommodated within the yoke. According to this arrangement, the length of the brushes is restricted by the inner periphery of the yoke. As the brushes wear during operation of the motor device, the life of the motor device is limited by the life of brushes.
It is therefore an object of the present invention to provide a motor device which is capable of employing lengthened brushes.
According to the present invention, a motor device has a motor unit and a reduction unit coupled with the motor unit. A commutator and brushes are disposed within a gear housing of the reduction unit located outside the opening of a yoke of the motor unit in an axial direction of the motor unit. Preferably, the gear housing is formed with a brush accommodating recess, at least a part of which is larger than an inner periphery of the yoke in a radial direction. The brushes are disposed within the brush accommodating recess. The brush accommodating recess is formed in a generally square shape, each brush is disposed along a diagonal line of the square shape.